QUANTITATIVE ESTIMATION lift centrated sulphuric acid and about 10 grams of anhydrous potassium sulphate. The object of the latter is to promote oxidation by raising the boiling-point of the liquid. The flask is clamped over wire-gauze and the contents boiled briskly until the liquid, which first darkens in colour, becomes clear and colourless or faintly yellow. When the decomposition is com- plete (-£—i hour), the flask is left to cool and the contents then diluted with 2—3 volumes of water. The flask is now attached to the distilling apparatus shown in Fig. 18. It is furnished with a double-bored rubber cork, through one hole of which a bulb adapter is inserted (to re- tain any alkali which may spirt upwards), the latter being con- nected with a condenser. The end of the condenser just dips below the surface of 25 c.c. of a half-normal solution of hydro- chloric or sulphuric acid, con- tained in a flask or beaker. A tap-funnel with a bent leg, con- taining about 30 grams of caustic soda in 60 c.c. of water, is inserted through the second hole in the cork. A few pieces of porous earthenware or granu- lated zinc are introduced into the flask to prevent bumping. After the apparatus has been fitted together the caustic soda tlc> l8' solution is run in slowly and the flask shaken. The liquid is then boiled briskly until no more ammonia is evolved (-|-—f hour). This should be ascertained by testing a drop of the distillate with red litmus paper. If the operation is complete, the liquid is titrated with half-normal 'sodium carbonate solution, using methyl orange as indicator. Example.—0*5151 gram acetanilide required 17*3 c.c. N/2 sodium carbonate :— 25 - 17-3 = 77- 77XO-OQ7XIOO = IQ.46 per cent_ 0-5151 if *Y'